Sensor systems are used, for example, in connection with safety systems in the motor vehicle sector. The sensor elements are implemented together with evaluation circuit components in the form of sensor chips that are produced in large numbers and provided with packaging. On the one hand, the packaging protects the sensor function and the circuit components, and on the other hand, it simplifies the installation of the sensor element at the particular point of use. A plastic molded housing having a metal plate situated over the sensor diaphragm and having a pressure connection opening is frequently used as packaging. This type of packaging may be manufactured simply and cost-effectively. It is also extremely stable and media-resistant.
As the measuring medium is soiled with dirt and particles in many applications, the pressure connection to the measuring system is usually designed in such a way that only the sensor diaphragm is exposed to the measuring medium while the other components of the sensor module, such as the electrical contacts, are not intended to come into contact with the measuring medium. To that end, the pressure channel of the connecting piece is situated in alignment with the pressure connection opening above the sensor module. The connection between the pressure channel and the pressure connection opening is sealed to protect the other components of the sensor module from the measuring medium.
This situation is illustrated in FIG. 1. Sensor module 10 shown here includes a sensor chip having a sensor diaphragm 1 for pressure detection. A metal plate 2 having a pressure connection opening 3 is situated above sensor diaphragm 1. Metal plate 2 is integrated in the top of molded housing 4 of the sensor chip. Electrical contacts 5 for the sensor chip are provided on the bottom of molded housing 4. Accordingly, sensor module 10 is mounted on a circuit board 11 in this case. The pressure connection of sensor module 10 to a measuring system is made via connecting piece 12 in the shape of a lid in which pressure channel 13 is provided. Connecting piece 12 is mounted above sensor module 10 in such a way that pressure connection opening 3 of sensor module 10 and pressure channel 13 of connecting piece 12 are situated in alignment with one another. This flange-type connection between pressure connection opening 3 and pressure channel 13 is sealed in this case using an annular seal 14 compressed in a planar manner between connecting piece 12 and the upper side of the housing of sensor module 10.
This annular seal must be kept permanently under compressive stress in order to ensure the sealing effect, which proves to be problematic. In practice, it has namely been shown that the compressive stress acting perpendicular to the sensor diaphragm may be transmitted to the sensor element via the packaging of the sensor module. This results in a corruption of the measuring signals. In addition, the electrical connection of the sensor module may also be damaged in this manner.